Staff: Mentor

As stewartcs indicated, the thermocouple could have simply failed, in which case it needs to be replaced. I'm not familiar with that T/C or Frame 9 turbine, but if it's hot (exhaust) this presumably would require that the unit be shutdown.

Is the thermocouple in the a well? Could the well have been breached (ostensibly due to erosion/corrosion)? Has the T/C reached it's lifetime or the min expected lifetime? Are there redundant T/C's?

Definitely contact GE they should be able to help you immediately. At least that is how it works at Rolls Royce with the industrial RB211 and Trend series. Also Astronuc makes a good point, maybe direct replacement is not an necessity usually there are two or three exhaust thermocouples and there should be standard protocol if it should be replaced immediately or not.

From what I've seen thermocouples do fail but more often than not it is the wiring/connectors. Check the readings from any points you can between monitoring system and the actual thermocouple. Probably just a loose connector caused by constant vibrations.

Whatever it is you are going to need to go through troubleshooting to find it.